Subject: Re: [Intel-gfx] [Announcement] 2015-Q3 release of XenGT - a Mediated
 Graphics Passthrough Solution from Intel
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
        Jike Song <jike.song@intel.com>
References: <53D215D3.50608@intel.com> <547FCAAD.2060406@intel.com>
 <54AF967B.3060503@intel.com> <5527CEC4.9080700@intel.com>
 <559B3E38.1080707@intel.com> <562F4311.9@intel.com>
 <1447870341.4697.92.camel@redhat.com>
 <AADFC41AFE54684AB9EE6CBC0274A5D15F7152DB@SHSMSX101.ccr.corp.intel.com>
 <564D78D0.80904@intel.com>
 <alpine.DEB.2.02.1511191529370.1107@kaball.uk.xensource.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
        "Tian, Kevin" <kevin.tian@intel.com>,
        "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
        "igvt-g@ml01.01.org" <igvt-g@ml01.01.org>,
        "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "White, Michael L" <michael.l.white@intel.com>,
        "Dong, Eddie" <eddie.dong@intel.com>, "Li, Susie" <susie.li@intel.com>,
        "Cowperthwaite, David J" <david.j.cowperthwaite@intel.com>,
        "Reddy, Raghuveer" <raghuveer.reddy@intel.com>,
        "Zhu, Libo" <libo.zhu@intel.com>, "Zhou, Chao" <chao.zhou@intel.com>,
        "Wang, Hongbo" <hongbo.wang@intel.com>,
        "Lv, Zhiyuan" <zhiyuan.lv@intel.com>,
        qemu-devel <qemu-devel@nongnu.org>, Gerd Hoffmann <kraxel@redhat.com>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <564DEF9A.3010901@redhat.com>
Date: Thu, 19 Nov 2015 16:49:46 +0100
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On 19/11/2015 16:32, Stefano Stabellini wrote:
> > In addition to Kevin's replies, I have a high-level question: can VFIO
> > be used by QEMU for both KVM and Xen?
> 
> No. VFIO cannot be used with Xen today. When running on Xen, the IOMMU
> is owned by Xen.

I don't think QEMU command line compatibility between KVM and Xen should
be a design goal for GVT-g.

Nevertheless, it shouldn't be a problem to use a "virtual" VFIO (which
doesn't need the IOMMU, because it uses the MMU in the physical GPU)
even under Xen.

Paolo
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